Chemotherapy Temporarily Affects The Structures Of The Human Brain

Researchers have linked chemotherapy with short-term structural changes in cognitive areas of the brain, according to a new study. Published in the January 1, 2007 issue of CANCER, a peer-reviewed journal of the American Cancer Society, the study reveals that within 12 months of receiving adjuvant chemotherapy, significant regions of the brain associated with memory, analysis and other cognitive functions were significantly smaller in breast cancer patients who received chemotherapy than those who did not. Within four years after treatment, however, there were no differences in these same regions of the brain.

While the development of chemotherapy has had substantial and beneficial impact on cancer survival rates, it is also linked to significant short- and long-term adverse effects. Gastrointestinal complaints, immunosuppression, and painful mucositis, for example, are the immediate risks of the treatment.

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Patients receiving chemotherapy have also long complained of problems with memory, problem-solving and other cognitive abilities. Although chemotherapy was thought not to affect brain cells due to the blood-brain barrier, recent clinical studies have confirmed declines in cognitive functions in patients receiving chemotherapy. Animal studies have shown physical changes in the brain and in neurons caused by chemotherapy drugs. In human studies, however, the little data that is available is only available through imaging and is not consistent in the long-term. In addition, lack of controls in studies makes it difficult discern cancer- versus drug-effects.

Led by Masatoshi Inagaki, M.D., Ph.D., of the Breast Cancer Survivors' Brain MRI Database Group in Japan, researchers used MRI to take high-resolution images and measure volumes in specific areas of the brain of breast cancer patients who received chemotherapy and those who did not one-year after surgery and three-years after surgery. In addition, they compared brains of cancer survivors one-year after surgery and three-years after surgery with healthy subjects.

They found that at one-year, patients treated with chemotherapy had smaller volumes in cognitively sensitive areas, such as the prefrontal, parahippocampal and cingulate gyri, and precuneus regions. However, at three-years post-surgery there was no volume differences. That there were no differences between cancer patients and healthy controls at any time point demonstrates that there is no observable cancer-effect in cognitive deficits.

The authors write that this study suggests that regional brain changes are observable within 12 months and correlate with receiving chemotherapy rather than a secondary effect of the cancer, although it cannot be concluded because of several limitations caused by the study design. However, these structural changes to the central nervous system were not sustained for patients three years after chemotherapy. The authors conclude that "these results lead to the idea that adjuvant chemotherapy could have a temporary effect on brain structure."